Transenamel and transdentinal cytotoxicity of carbamide peroxide bleaching gels on odontoblast-like MDPC-23 cells

Soares DGS, Ribeiro APD, Sacono NT, Coldebella CR, Hebling J, de Souza Costa CA. Transenamel and transdentinal cytotoxicity of carbamide peroxide bleaching gels on odontoblast‐like MDPC‐23 cells. International Endodontic Journal, 44, 116–125, 2011. Aim To evaluate the transenamel and transdentinal cytotoxicity of bleaching gels based on carbamide peroxide (CP) on odontoblast‐like cells after different contact times of the products with enamel. Methodology Enamel/dentine discs were obtained from bovine incisors and placed in artificial pulp chambers. Bleaching gels containing 10% or 16% CP were applied for 8 h day−1 on the enamel side of the discs during periods of 1, 7 or 14 days. Deionized water and artificial saliva served as controls. The extracts (culture medium plus bleaching gel products that diffused through the discs) were collected and applied on previously cultured MDPC‐23 cells for 1 h. Cell metabolism was evaluated by the MTT assay, and the data were analysed statistically by one‐way anova and Tukey’s test (α = 0.05). Cell morphology was analysed by SEM. Results There was no significant difference (P > 0.05) between the controls and the groups bleached with 10% CP gel. In the groups bleached with 16% CP gel, however, cell metabolism decreased significantly (P 0.05) between 1, 7 or 14 applications of the gels for either of the CP concentrations. Conclusion Regardless of the number of applications on an enamel surface, the 10% CP bleaching gel did not cause transenamel and transdentinal cytotoxicity to the MDPC‐23 cell cultures. However, diffusion of products from the 16% CP gel through enamel and dentine and cytopathic effects to the pulp cells occurred even after a single application of this product on enamel.